Seed pellets and process for their manufacture

ABSTRACT

The seed pellets have a core which contains grains of seed, organic substrate, loess, organic fertilizer, fungicides and, possibly, pesticides, and a wetting agent which promotes surface wettability. At least one bitter substance may also be present and made to cover the core in the form of a coat, or be distributed within the core. The core is furthermore provided, with a semipermeable coat, which consists of at least one starch and/or latex. The loess acts as a binding agent which serves to intimately bind the various constituents of the core to each other, and to act as a water storing agent in addition to the organic substrate. The semipermeable coat also contributes to the improvement and control of water conservation. Thus the pellets may be made to include sensitive seeds too which require much water for germination and/or may be sown in relatively dry regions and, furthermore, are resistant to breakage and abrasion.

BACKGROUND OF THE INVENTION

The invention relates to seed pellets each containing at least one grainof seed and an organic substrate.

In Swiss patent specification No. 561 021 there was revealed a seedpreparation (compound) produced by mixing 20 kg of poor-grade grass,so-called mulch, and 1 kg of crude cellulose flakes, and drying themixture at a temperature of about 140° C. until the residual watercontent is only 15% by weight. The following substances are then addedto this premixture, the percentages given representing % by weight,relative to the dried grass.

1.5% of 1,4 butanediol as hydrophilic constituent

2% of seed

0.25% of sodium alginate

0.25% of polyacrylic amide

0.25% of octylphenyl octoglycol ether

0.25% of fungicide

0.5% of nutrient salts

This mixture can be compressed to moulded bodies, so-called pelletswherein the sodium alginate and polyacrylic amide act as binding agents.

According to Swiss patent specification No. 561 021 such pellets areprovided with grass seeds and, in practice, with clover seed(leguminosa) too. These pellets, however, are not suitable for seedswhich require relatively much water, and/or are sown in extremely dryareas, such as the seed of dry rice and of many other cultivated plantsor forest seeds. The dried grass, of which the percentage by weight inthe pellets is of the order of 90%, can give off only about one-third ofthis water content of about 15% by weight which exists therein, i.e.,only about 5% of the weight of the dried grass. Furthermore, the pelletsknown lose relatively much water to the environment in a dryenvironment. A further disadvantage of the seed pellets according toSwiss patent specification No. 561 021 resides in the fact that thedried grass particles, seeds and other pellet constituents pressed toform pellets are held together only relatively loosely so that theybreak readily during transport and on sowing, and lose material throughabrasion.

SUMMARY OF THE INVENTION

An object of the invention is to provide seed pellets which eliminatethe disadvantages of the known seed pellets. The pellets are to besuitable particularly for applications where the seeds in the pelletsrequire much water and/or where the pellets are to be sown in arelatively dry environment. Furthermore, the seed pellets are preferablyto have high breaking strength and high resistance to abrasion.

This object is achieved by means of seed pellets of the aforedescribedtype which are characterized according to the invention by containingloess. This object, moreover, is achieved by means of seed pelletscharacterized according to the invention in that they have a corecontaining at least the aforedescribed constituents and a semipermeablecoat enclosing said core. Advantageous embodiments of the seed pelletsare indicated in the relevant dependent claims relating to the seedpellets.

The invention, furthermore, relates to a method of producing seedpellets wherein seed pellets are formed from at least one seed and anorganic substrate. The method according to the invention ischaracterized in that the organic substrate is mixed with loess beforethe seed pellets are pressed. The invention relates furthermore to amethod of the aforedescribed type which is characterized according tothe invention in that the cores formed of at least the aforementionedconstituents, are covered by a semipermeable coat.

The organic substrate may be produced of non-woody plant material,advantageously also containing water, but being just dry enough to beground well and/or crushed mechanically in some other manner, and thenbe mixed well in the form of particulate material with the seeds, loessand other desirable constituents, and finally agglomerated toagglomerated particles. The organic substrate may be formed, forexample, of dried grass, straw and/or algae and/or leaf material. Theseraw plant materials are dried, in a drying device, unless they havealready been sufficiently dried by natural drying processes, said dryingdevice comprising for example a drying tower, in which hot air is passedthrough the plant material to be dried. The material for the organicsubstrate may be heated during the drying process or possibly in aseparate sterilizing process to a temperature of at least about 100° C.and not more than about 180° C. and for example, to between 130° and150° C., the material to be sterilized thereby. If the plant materialshould have been rendered too dry through natural drying processes, itis also possible to moisten the plant material, which could be donebefore and/or after the comminution. By drying and/or possiblymoistening and comminuting the plant material, a particulate organicsubstrate can be formed, of which the water content is at least 10%,preferably at least 12%, but not more than 20%, preferably not more than18% and, for example, about 15% of the total weight.

The plant material may be ground, for example, by using a beater mill toform particles of suitable sizes, and then be sifted, the excessivelylarge and the excessively small particles being removable during thesifting process. In this manner a particulate, organic substrate of amore or less uniform particle size can be formed. The characteristicsizes for the substrate particles may be not more than 1 mm andpreferably not more than about 0.5 mm, at least on the average, andpreferably for the majority of the particles or even for all of theparticles. The characteristic sizes for the organic substrate particles,furthermore, should be at least about 0,1 mm on an average, andpreferably for the majority of the organic substrate particles or evenfor all of the particles, so that the particulate material will notbehave like dust.

The loess used is preferably a degenerated loess. Degenerated loess isformed in surface earth areas where it is subjected to the action oforganisms and is partially decomposed, so that it contains at least onenatural nutrient and, in general, several such nutrients. It is possibleto use such degenerated loess, as may be found, for example, to occur asoverburden and waste product when processing loam or clay in the courseof manufacturing brickworks products. Such loess which covers loam orclaylike substances required for the production of brickworks products,has a consistency too low to be used for the production of brickworksproducts, and therefore may be obtained relatively cheaply. However,non-degenerated and more or less nutrient-free loess may also be used,in which case, however, relatively large quantities of fertilizer mustbe added. The loess may be sifted while it is produced, to removeexcessively large lumps or other particles too large. The characteristicsize for the loess particles may be not more than 0.1 mm and preferablynot more than 0.05 mm, at least on the average, and preferably for themajority of the particles, or even for all of the particles. Loesspossesses large particle surfaces suitable for water to adhere thereto,its ability to store water being the greater, the finer the loess, andthe larger, correspondingly, its particle surface. Loess feels dry, muchlike a dry material, even if it contains relatively much water, and maytherefore be mixed well with the organic plant substrate, the seeds andother desired constituents, even if its water content is relativelyhigh. The water content of the loess used for forming the seed pelletsshould be at least about 10% and preferably at least 12% of the moistloess weight i.e., of the total loess weight. The water content of theloess can amount to not more than about 19 or 20% by weight or, it mayeven go as high as at most about 30% by weight. The loess collected mayalso be moistened and/or dried for forming the pellets.

The particulate organic plant substrate and the equally particulateloess and the seeds are intermixed for forming the seed pellets. Atleast one particulate fertilizer, such as an organic fertilizer, forexample, guano is peferably added to this mixture. This fertilizer orpart thereof may possibly be admixed to the loess before the loess isintermixed with the organic substrate. At least one fungicide, andadvantageously a mixture of fungicides and/or possibly at least onepesticide, or a mixture containing several of these may be intermixedwith the mixture. Furthermore, it is of advantage to admix a wettingagent to the mixture, the wetting agent consisting, for example, of atleast one hydrophilic chemical and/or an algae derivative calledaluginate, and to be provided for reducing the surface tension of thewater coming into contact with the outer surfaces of the finishedpellets, so that any water reaching the pellets, such as dew or raindrops, may rapidly and possibly uniformly spread across possibly largeportions of the pellet surfaces.

The seeds, the organic substrate, the loess, the preferably providedfertilizer, the preferably provided fungicides and possibly pesticidesand the preferably provided wetting agent may be intermixed by means ofa mixing apparatus, so as to produce a possibly homogenous mixture. Thismixture may be moulded, compressed and agglomerated by means of apressing device called compactor to form pressed bodies or agglomeratedparticles each of these to contain at least one grain of seed, andpreferably a number of grains of seed. The pressed bodies oragglomerated particles may contain, depending on the type and size ofthe grains of seed, at least 2, preferably at least 4 or up to not morethan 15 grains of seed, the grains of seed to be distributed preferablyuniformly over the entire volume of the pressed bodies or agglomeratedparticles. The water-containing loess acts as binding agent during andafter compressing the pressed bodies or agglomerated particles, saidbinding agent being effective to relatively firmly bind the otherconstituents of the pressed bodies together and to itself. Since heatmay be released during the pressing process it is necessary to designthe pressing device and to carry out the pressing process in a manner tokeep the temperature of the different constituents of the pressed bodiesor agglomerated particles, and in particular the temperature of thegrains of seed contained therein from ever exceeding 35° C. andpreferably from ever exceeding 30° C., so that the germinating abilityof the grains of seed will not be affected. Keeping the temperature lowduring pressing may contribute, moreover to keep the water losses low,so that the water contained in the organic substrate and the loess maybe at least approximately the same after pressing, as it was beforepressing.

After the pressed bodies or agglomerated particles have been pressed orpossibly while they are being pressed, they may be cooled down again tonormal room temperature of about 20° to 25° C., for example, by passingan air stream through them, or by just exposing them to ambienttemperature.

To provide them protection against animals feeding on them, the seedpellets may be provided with at least one bitter, preferablynon-poisonous substance, as commercially available as seed-protectingpreparation (product). The bitter substance may be admixed to themixture comprising the grains of seed, the organic substrate and theloess, before the pressed bodies or the agglomerated particles arepressed. However, it is also possible to advantageously apply the bittersubstance partly or wholly, to the pressed bodies or agglomeratedparticles, after they have been produced, to make each such part form acore, having its entire surface covered with a coat containing thebitter substance. The core will then preferably have a lowerconcentration of bitter substance than the coat containing the bittersubstance, or it may contain no bitter substance at all.

A second, outer, film-like coat to extend over the entire outer surfaceof the pellet and forming the outer boundary thereof may be applied tothe preferably provided first, inner coat, containing the bittersubstance, said outer coat to serve for influencing the passage of thesubstance across the outer surface of the finished seed pellet. Thissecond coat should be semipermeable, so that water from the outside maypenetrate through it into the core of the respective seed pellet, andthat it may prevent, at least partially and preferably entirely, atleast part of the water-soluble substances contained in the core, inparticular the fungicides and/or pesticides, and preferably thenutrients too, and preferably all of the water-soluble constituents ofthe core, from leaving the pellet. Furthermore, the second coat shouldbe enabled to inhibit and possibly prevent at least the escape of liquidwater and preferably the escape of water vapour too from the pellet, atleast in situations, in which the respective seed pellet is located in adry environment. However, the second coat may be gas-permeable to adegree, to allow air required for the seed to germinate and for thegerm-buds to grow, to penetrate from the outside into the pellet. Inaddition, the second coat must be made to interfere with the germ-budsgrowing out of the seed pellet, as little as possible. The second coatmay consist, at least partially or entirely, of a porous materialadapted to swell up in a moist environment and to make its pores widen,and to contract in a dry environment and to make the pores narrowerand/or to close entirely. A material having such properties and referredto in the following as semipermeable material, may be, for example, anatural latex and/or at least one starch. Suitable starches are, forexample, the starches of grain seed, such the albumen-rich grain starchand maize starches, or the starches from the seeds of carob, also knownas St. John's bread.

When the pressed bodies are to be coated with the bitter substance, thelatter substance may be dissolved, for example, in an aqueous solventand sprayed onto the pressed bodies in the form of a solution, which maycontain other additives. The bitter substance-like coat can then beobtained by drying the sprayed-on solution. The semipermeable material,i.e. the starch and/or latex may also be sprayed onto the pressed bodiesin the form of a preferably aqueous solution, and then dried. Air may bepassed for example through the sprayed pressed bodies, so as to dry thecoats sprayed-on in solution.

An additional coat of bitter substance may be applied to the secondsemipermeable coat. One could even provide several coats, so that coatsof bitter substance would alternate with semipermeable coats. It wouldalso be possible to use an aqueous solution containing both the bittersubstance and the semipermeable material, and spray it onto the pressedbodies and dry it subsequently. In this case a coat enclosing the coremay be created, the coat containing the bitter substance and thesemipermeable material. Should it be necessary or advantageous for theparticular type of bitter substance and/or semipermeable material, theymay be sprayed onto the pressed bodies in the form of a nonaqueoussolution or a suspension, or applied in some other manner.

The percentage of the grains of seed relative to the weight of thepellet cores and relative to the but slightly greater total weight ofthe pellets may amount to about at least 0.5% or perhaps at least 1.5%up to not more than about 5% or not more than about 4% by weight. Thewater content of the organic substrate and of the loess in the completedpellets may be about equal to the respective values specified before forthe respective raw materials. The percentage of weight the organicsubstrate and of the loess, relative to the total weight of the pelletsdepends, of course on the momentary water content of the organicsubstrate and of the loess, respectively, and may be about 30% or moreand about 60% or less by weight of the cores or of the whole pellets.The percentage of the substrate and the loess, preferably each amountsto about 40% or more, and preferably about 55% or less by weight of thepellet cores or of the whole pellets. The percentage of thewater-containing organic substrate may be, for example, about 44 to 48%and that of the water-containing loess about 46 to 50% by weight of thepellet cores or of the whole pellets. The percentage weight of the loessis thus, for example, approximately equal to and/or slightly larger thanthat of the organic substrate. The percentage of natural nutrientscontained in a degenerated loess is dependent on the origin of theloess, and amounts to approximately 2% or less and usually to 1% or lessby weight of the total loess. The percentage of the preferably organicfertilizer added may be at least about 1% by weight of the loess or atleast about 0.5% by weight of the whole pellet, and not more than about4% by weight of the loess or not more than about 2% by weight of thepellets, and, for example, not more than or approximately 2% by weightof the loess or approximately 1% or less by weight of the whole pellet,depending on the content of natural nutrient in the loess. The totalpercentage of nutrient resulting from the preferably present naturalnutrient in the loess and the additionally added fertilizer may then beabout 0.5 to 2.5% by weight and, for example, about 1% by weight of thewhole pellet, which corresponds to about 2% by weight of the loess. Thepercentage of fungicides and pesticides, together, may be about 0,2 to0,4% by weight of the cores or of the whole pellets.

The percentage of wetting agent may be typically at least 1% and, forexample, at least 1.5% and not more than about 2% by weight of the coresor of the whole pellets. The percentage of bitter substance present inthe cores and/or the coats may be at least about 0.1% not more thanabout 0.5% and preferably not more than 0.3% by weight of the cores orof the whole pellets. The percentage of semipermeable material may be atleast 0.2% not more than 1% and, for example, about 0.4 to 0.6% byweight of the whole pellet, so that the percentage of the otherconstituents of the pellets may accordingly, be at least 99% and, forexample, about 99.4 to 99.6% by weight of the whole pellet. If thesemipermeable material forms a film-like coat by itself, i.e. withoutbitter substance, its thickness may be, for example, not more than about0.1 mm or less.

The loess arranged to substitute for at least about half of the organicplant substrate of the pellets known from Swiss patent specification No.561 021, is made to act both as binding agent and as water retainer. Theloess is effective to create a firm and more abrasion-resistant bond ofthe pellet components, than the binding agent of the pellets disclosedin the Swiss patent specification No. 561 021; this may be attributed tothe fact, that the percentage of loess contained in the pelletsaccording to the invention may be made substantially larger than thepercentage of binding agent present in the known pellets. However, theloess primarily possesses the advantage of very good water-retainingproperties; it is not only able to absorb relatively much water, but togive off this water again almost entirely, more specifically up to apercentage amounting to about 2 to 3% of its own weight. When using adegenerated loess, as loess, as is preferably the case, the nutrientspresent in this loess will promote the growth of the germ-buds.

The semipermeable coat is also able to contribute to improving the waterretention, by the fact, that its pores narrow or close in a dryenvironment, and widen in a moist environment. In addition, thewater-soluble substances present in the pellet may produce an osmoticeffect, so that in a dry environment not more than a small amount ofwater will leave the pellet through the semipermeable coat, while onwetting the pellet water can well penetrate into the pellet from theoutside. In addition the coat may possibly contribute to improving thecohesion of the single pellets and their resistance to abrasion.

A substantial advantage of the present invention consists in that inaddition to pellets including grass and clover seeds (as is knownalready), pellets which germinate well and include seed of many otherwild and cultivated plants, such as forest seed, seed of dry rice,mealies, wheat, sesame and pulses may be produced Good results may beobtained when sowing the pellets in relatively dry areas. In addition,the pellets are resistant to breakage and abrasion during transport and,sowing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The pellets according to the invention may have, for example, thefollowing composition:

2% by weight of seed of Bermuda grass

48% by weight of natural, untreated, degenerated, water-containingloess, for example from "Bruderholz", a wooded area near Basle,Switzerland,

1% by weight of fertilizer, namely Guano

0.3% by weight of at least one fungicide and/or possibly a pesticide,for example of a fungicide/pesticide-mixed product produced by the firmSandoz AG, Basle, Switzerland, under the trademark CAPTAFOL

1.5% by weight of a surface-active, hydrophilic wetting agent, forexample of the chemical preparation (product) based on glycerin,obtainable under the trademark SANDOVIT from the firm Sandoz AG, Basle,Switzerland

0.3% by weight of a bitter substance, for example, a seed protectionpreparation (product) produced under the trademark CURB by the firmSphere Laboratories (LONDON) Ltd., London, Great Britain, anddistributed in Switzerland by the firm Pluss-Staufer AG, at Oftringen

5% by weight of natural latex as semipermeable material

remainder (46.4% by weight) hay flour as organic substrate.

The grains of seed, the hay flour, the loess, the fertilizer, thefungicide and possibly the pesticides, the wetting agent and, optionallyalso all or part of the bitter substance were thoroughly intermixed withone another in a mixer. Pressed bodies weighing from of 3.5 to 7 g werethen produced of this mixture by means of a pressing device comprisingtwo form cylinders rotating in opposite directions. These pressed bodieswere coated with the bitter substance, unless this substance had beenintroduced before into the mixture, and with latex. During the entireprocess of production of the pellets the temperature must never beallowed to exceed 30° C.

In another example the pellets had the following composition:

4% by weight of small graded maize seed

47.4% by weight of degenerated loess, for example from "Bruderholz" nearBasle, Switzerland

0.3% by weight of the fungicides mentioned in the first example, and/orpossibly the pesticides

1.5% by weight of the wetting agent mentioned in the first example

1% by weight of fertilizer, specifically Guano

0.3% by weight of the bitter substance mentioned in the first example

0.5% by weight of albumen-rich grain starch as semipermeable material

remainder (45% by weight) of straw flour, for example maize straw, asorganic substrate.

The pellets may be produced in a manner similar to that described in thefirst example, i.e., by first mixing the constituents serving forforming the cores preferably homogeneously, and then pressing andagglomerating the mixture in a pressing device called a compactor, toform pressed bodies or agglomerated particles. The bitter substanceitself may be admixed to the mixture serving for forming the cores ormay be applied, partially or entirely, as a coat to these cores, afterthe latter have been formed. The grain starch, on the other hand, isapplied to the cores as a coat, so that the starch, possibly togetherwith the bitter substance, will form a coating bounding the pellets onthe outside.

The water contained in the organic substrate and the loess of the seedpellets produced in accordance with the above examples may lie withinthe previously specified ranges, and is selected to prevent the seedsfrom germinating, as long as the seed pellets are stored in a dryenvironment in an air-permeable packing, for example, in jute bags. Theseed pellets may be sowed manually or mechanically or dispersed from anaeroplane. When the moisture in the environment of the pellets exceeds aspecified limit, the pellet will absorb water, while at the same timethe water content of the organic substrate and/or the loess may rise tothe point of saturation. The seed will then start to germinate, while atthe same time the bitter substances will prevent the germ-buds frombeing eaten by animals and the fungicides and/or the pesticides willprotect the seed from fungi and similar parasites.

The pellets, of course, may be provided with a multitude of other typesof seed in an analogous manner. Furthermore, the hay or straw flourspecified as plant substrate in the two previous examples, may besubstituted by ground algae or leaf material or by any non-woody plantsubstance. The bitter substance specified in said examples may bereplaced, for example, a soja-based bitter substance. The pellets couldalso include as hydrophilic wetting agent, a fattyacid-glycerine-derivative and/or a formaldehyde resin and/or an algaederivative, called aluginate, in place of or in addition to the wettingagent specified in the examples.

I claim:
 1. A seed pellet comprising a core and a semipermeable coat enclosing said core; wherein said core comprises at least two seed grains, and an organic substrate which comprises a non-woody plant material, loess, and a wetting agent; and wherein said semipermeable coat is adapted to allow water to penetrate from outside each said pellet into said core.
 2. A seed pellet according to claim 1, wherein the proportion of loess is at least 30% by weight and not more than 60% by weight, and wherein the proportion of organic substrate is at least 30% by weight and not more than 60% by weight of the total seed pellet.
 3. A seed pellet according to claim 1, wherein the loess is degenerated and contains at least one natural nutrient.
 4. A seed pellet according to claim 1, further comprising at least one organic nutirent; at least one of a fungicide and pesticide; and a wetting agent for reducing the surface tension of water.
 5. A seed pellet according to claim 4, wherein the proportion of the wetting agent is at least 1% by weight and not more than 2% by weight of the total seed pellet.
 6. A seed pellet according to claim 1, further comprising at least one bitter substance.
 7. A seed pellet according to claim 1, wherein the semipermeable coat comprises one of latex and at least one starch.
 8. A seed pellet according to claim 1, wherein the proportion of the semipermeable material present in the semipermeable coat is at least 0.2% by weight, and is not more than 1% by weight.
 9. A seed pellet according to claim 1, wherein at least one of the non-woody plant material and the loess further comprise absorbed water.
 10. A seed pellet according to claim 9, wherein the water content of the organic substrate is at least 10% by weight and at most 20% by weight, and the water content of the loess is at least 10% by weight and at most 20% by weight.
 11. A seed pellet according to claim 1, wherein the organic substrate comprises at least one of grass, straw, algae and leaf material.
 12. A seed pellet according to claim 1, wherein the core comprises at least four seed grains.
 13. A seed pellet according to claim 1, wherein the proportion of loess is at least 40% by weight and not more than 55% by weight of the total seed pellet.
 14. A seed pellet according to claim 1, wherein the semipermeable coat further comprises a non-poisonous bitter substance.
 15. A seed pellet according to claim 1, wherein both the core and the coat additionally comprise a non-poisonous bitter substance.
 16. A seed pellet according to claim 1, wherein the coat comprises a porous material adapted to swell up in a moist environment making its pores wider, and to contract in a dry environment making the pores narrower, so that water from the outside of the pellet may penetrate through the coat into the core on wetting, and that the escape of water out of the core is inhibited in a dry environment.
 17. A seed pellet according to claim 1, comprising at least 1.5% by weight of seed and having a weight of at least 3.5 grams.
 18. A seed pellet comprising a core and a semipermeable coat enclosing said core, wherein the core comprises a mixture of 1.5% by weight to 4% by weight of seed, 0.2% to 0.4% by weight of at least one of a fungicide and pesticide, 1.5% to 2% by weight of a wetting agent, 44% to 48% by weight of organic substrate, 46% to 50% by weight of degenerated loess and organic nutrient, and 0.1% to 0.3% by weight of a non-poisonous bitter substance, wherein all percentages refer to the whole pellet, and wherein the coat is adapted to inhibit the escape of water out of the core in a dry environment and to let water penetrate from the outside into the core on wetting.
 19. A seed pellet according to claim 18, wherein the core further comprises at least two seed grain, wherein the organic substrate comprises non-woodened plant material, and wherein the loess is degenerated and contains at least one organic nutrient.
 20. Method of producing a seed pellet, comprising the steps of preparing a mixture by intermixing grains of seed, an organic substrate comprising non-woody plant material, loess, a wetting agent and at least one of a fungicide and pesticide; pressing the mixture to form a core comprising at least two seed grains; and providing said core with a semipermeable coat adapted to inhibit the escape of water out of the core in a dry environment and to let water penetrate into the core on wetting.
 21. Method according to claim 20, further comprising the step of drying the plant material before the preparation of the mixture.
 22. Method according to claim 20, wherein preparing the mixture comprises the additional step of forming the organic substrate by grinding at least one of grass, straw, algae and leaf material.
 23. Method according to claim 20, wherein pressing the mixture to form the core is accomplished by means of rotating form cyclinders.
 24. Method according to claim 20, wherein providing the coat is accomplished by spraying a liquid material onto the core followed by drying said sprayed core. 